Funny you should ask, as we were just able to do this with Azure, basically just for fun - we did an export to VHD, then copied VHD to Azure, attached to a VM, powered on... and it worked. We were actually quite shocked, as this was totally unexpected. However, keep in mind that this was a very basic Windows desktop with stock Windows drivers, which perhaps contributed to a success.
Generally speaking, you can expect anything like this to fail in over 90% of cases, because each Windows installation has extremely deep tie-ups into hardware via drivers, and can only survive certain type of hardware changes automatically (and only a few at a time). But since in case of going to a hypervisor, virtually every hardware changes (pun intended), in vast majority of cases Windows will simply refuse to boot due to those rivers brought from physical system screwing everything up.